Hi Alexey,
>Date: Fri, 21 May 1999 10:39:07 +0400
>From: "Alexey Zhukov" <[EMAIL PROTECTED]>
>
>I want to make an assumption about the GraphicsContext3D.readRaster().
>
>There are two parts of Java3D color buffer: back and front one (Java3D
>operates in double-buffered mode). OpenGL glReadPixels() (readRaster() calls
>glReadPixels()...) reads color data from the back buffer by defaults (the
>behavior is controlled by glReadBuffer() function - Java3D Raster.setType()
>analogue). Generally, the content of the back buffer is undefined when the
>swap operation is complete (there are two possible cases of the back buffer
>content: blit - the buffer remains as is; and flip - the buffer contains
>previous frame and/or garbage). So, it seems to me the pixels reading after
>the swap is incorrect. The right place for this operation is the
>Canvas3D.postRender() method.
Java 3D reads pixels from the front buffer so reading it from postSwap is
usually the correct place to do it. calling readRaster from postRender
will result in the previous frame being read.
>Off-screen rendering.
>
>Why? Rendering to off-screen in system memory is impossible for most 3D
>hardware, so such rendering will be in software only or in hardware with
>readRaster() call. All that you need to produce large high-quality images is
>available today with hardware acceleration support. Don't try to produce
>large image at one rendering cycle. Divide the image by manageable parts,
>render them with readRaster() call in postRender(), then combine them into
>the final large. I think it's possible by using mixed-mode rendering.
This may be possible, but is inconvenient. Off-screen rendering is
very high on our list of features for the next (1.2) release of Java
3D.
--
Kevin Rushforth
Java 3D Team
Sun Microsystems
[EMAIL PROTECTED]
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